This invention relates in general to the joining of composite parts into a finished product and in particular to a new and useful method of sewing a seat cover into a foamed plastic panel of honeycombed cells.
A similar process for fabrication of seat covers with honeycomb cells is described in German patent DE-PS No. 33 04 343, in which striplike segments of foam plastic provides the filling of cells. It is introduced between a lower piece of material and an upper piece of material by means of guide channels, the upper piece of material lying around the lengthwise edges of the segments of foam plastic. Then, the cells are simultaneously sewn up on a multiple needle sewing machine. With seat covers manufactured in this way, the two seams lying in each recess between two cells will always be openly visible, so that this process is not suitable for manufacture of seat covers with cells in which the seams are to be concealed for optical reasons or for better durability.
U.S. Pat. No. 2 183 249 indicates a machine for the manufacture of seat covers which comprises prefabricated upper material segments, a bottom material fed from a supply reel, and many striplike elastic insert pieces lying between the layers of material. The layers of material are folded riblike between the insert pieces and the edges of the fold project on the lower piece of material. Then, the projecting portion of the fold is sewn up with a blind stitch by an appropriate number of sewing heads at the same time, so that many adjoining padded cells are formed on the upper side of the finished seat cover and the seams are quite invisible.
A serious defect of the seat covers made in this way is the fact that the seams under prolonged and heavy use are permanently stretched, so that gaps are formed between the originally adjacent segments of upper material in the region of the seam and as a result the threads of the seam become visible.